I presume you know that [itex]sin(\pi/3)= \frac{\sqrt{3}}{2}[/itex] and [itex]cos(\pi/3)= \frac{1}{2}. From there you can use the sum rules: [itex]sin(a+ b)= sin(a)cos(b)+ cos(a)sin(b)[/itex] and [itex]cos(a+ b)= cos(a)cos(b)- sin(a)sin(b)[/itex].